Correct,
a primary key is used to uniquely identify each row in a table. It can
either be part of the actual record itself , or it can be an artificial
field (one that has nothing to do with the actual record).
A primary key can consist of one or more fields on a table. When multiple
fields are
A Primary key constraint can be defined at various levels:
* Primary key constraint defined at column level
Syntax: Column Name datatype(size) Primary Key
* Primary key constraint defined at table level
Syntax: Primary key (Column Name, Column
Yes, but few exceptions;
Column level constraints are applicable to that column only, whereas table
level constraints are used to define composite keys like primary key for the
combination of two or more columns in a table.
column level constraints contain all types of constraints (like, not
Hi David, all!
David Stoltz wrote:
Actually,
That table isn't supposed to have a PK, so I removed that, and it
works...same effect you suggested.
Even if you currently don't need a primary key in that table, IMO you
should still define one. Use some 'id_testresult' column with an
Hi Folks,
I use an online SQL Design tool to design my tables, etc. This generates
script code that I can run in phpMySQL to create the tables, etc.
The below code is causing an error - see below:
CREATE TABLE `testresults` (
`id_employees` INTEGER DEFAULT NULL ,
`id_test_test`
Hi,
default cannot be used with primary key.
mysql CREATE TABLE `testresults` (
-
- `id_employees` INTEGER DEFAULT NULL ,
- `id_test_test` INTEGER DEFAULT NULL ,
- `testdate` DATE DEFAULT NULL ,
- `result` VARCHAR( 10 ) DEFAULT NULL ,
- `resultsdescription` MEDIUMTEXT
David,
You did not define a primary key for the table.
The PRIMARY KEY ( ) is expecting a column name inside the ( )
Mike
At 11:21 AM 6/23/2010, David Stoltz wrote:
Hi Folks,
I use an online SQL Design tool to design my tables, etc. This generates
script code that I can run in
creation fail
Hi,
default cannot be used with primary key.
mysql CREATE TABLE `testresults` (
-
- `id_employees` INTEGER DEFAULT NULL ,
- `id_test_test` INTEGER DEFAULT NULL ,
- `testdate` DATE DEFAULT NULL ,
- `result` VARCHAR( 10 ) DEFAULT NULL ,
- `resultsdescription
